Metal forming die elements



May 27, 1969 R. F. Moi/ER METAL FORMING n11: ELEMENTS Sheet Filed Sept.17, 1965 //vv/v 70/? ROBERT FRANKLIN MOVE? ATTORNEY United States PatentUS. Cl. 83658 12 Claims ABSTRACT OF THE DISCLOSURE Die elementsfabricated from pre-stressed organic polymers. A bore is provided in amass of organic material and thereafter a core larger in area than thebore is forced into the bore.

This invention relates to metal forming die elements and moreparticularly to the punch element and/or the die element, fabricatedfrom a pre-stressed organic polymer.

An object of the present invention is to provide a metal forming punchor die element fabricated from a prestressed organic polymer incooperation with a metal fabricated element.

Another object of the present invention is to provide an organic polymerpunch or die element in pre-stressed condition for cooperative matingwith its companion element.

And still another object of the present invention is to provide a massof an organic polymer in a pre-selected geometric shape and of apreselected durometer condition with a core of organic polymer having ahigher durometer condition than the mass, to change and control thecomprehensive sensitivity of the surface of the mass throughpre-stressing the mass by means of the core and by means of thedurometer condition of the core.

In prior art practice metal was formed by being subjected to the actionof a steel punch striking the metal blank against the mating steel die.

Recent practice developed the substitution of an oragnic polymer as thedie element which cooperated with a metal punch. A defect in thispractice has been the lack of detail reproduced in the metal blank bythe metal punch. Another drawback in this practice was the extremelylimited productive life of the organic polymer die element.

The present invention was developed to overcome these and other inherentdeficiencies in the prior practice.

Other objects of the present invention will become apparent in part andbe pointed out in part in the following specification and claims.

Referring to the drawings in which similar characters of referenceindicate corresponding parts in all the figures:

FIGURE 1 is a perspective view of the machine used to pre-stress theorganic polymer.

FIGURE 2 is a vertical cross sectional view taken on line 22 of FIGURE1.

FIGURE 3 is a perspective view of a block of organic polymer beforepre-stressing and for use in a die set. (Core not inserted.)

FIGURE 4 is a fragmentary, cross sectional view illustrating theinsertion of a core into block to accomplish pre-stressing of the block.

FIGURE 5 is a fragmentary, cross sectional view, illustrating the corelocked in the block by means of the enlarged diameter of the coredisplacing the softer wall of the bore in the block.

FIGURE 6 is a horizontal cross sectional view taken on line 44 of FIGURE3 after the block shown in FIGURE 3 is pro-stressed.

FIGURE 7 is a side elevational view of die set with the pre-stressedblock of organic polymer in use as a female die member.

3,446,107 Patented May 27, 1969 FIGURE 8 is a horizontal view throughthe die set taken on line 88 of FIGURE 7.

FIGURE 9 is a side elevational view of a die set wherein a smooth innerand outer surface metal tube is converted into a corrugated tube.

FIGURE 10 is a horizontal view through the die set taken on line 10-10of FIGURE 9.

FIGURE 11 is a vertical cross sectional view taken on line 11-11 ofFIGURE 10.

FIGURE 12 is a view similar to FIGURE 11 showing the organic polymerblock, used as a die member, in compressed condition in a die set.

FIGURE 13 is a modified form of organic polymer block used in anembossing machine, schematically illustrated.

Reference is now made to FIGURES 3, 4, 5 and 6 of the drawings whereinis illustrated a die element fabricated from a generic specie of organicpolymer material. One such organic polymer material is polyurethanewhich inherently possesses the physical characteristics of uniformexpansion and uniform construction when compressed or when force isremoved therefrom.

A polyurethane material having the following physical characteristicsprovides a satisfactory die block for the purposes which willhereinafter appear:

A durometer reading approximating seventy An elongation potential ofapproximately six hundred fifty percent (650%) but not less than fivehundred percent (500%). A normal elongation of two hundred percent ateighteen pounds per square inch pulling force. A minimum tensilestrength of forty-three hundred pounds per square inch. One suchpolyurethane material is commercially known as Elastacast.

Applicant has utilized these natural characteristics and modified themin the following manner.

The die block, generally indicated by reference numeral 10, ispreferably, in one embodiment, rectangular in shape and provided with anaxial opening 11. The axial opening or bore 11 is approximately fiftypercent (50%) in diameter to the width of the die block. Opposite endsof axial bore 11 are provided with countersunk areas 12.

A core 13 is inserted into opening 11 in order to prestress die block10. Die block 10 is pre-stressed to create a desired degree ofcomprehensive sensitivity in the outside surfaces 10A, 10B, 10C, 10D ofdie block 10.

It has been found that a core fabricated from wood, iron, steel or othernon-compressible material defeats the object sought in prc-stressing dieblock 10, namely, controlling the degree of compressive sensitivity inthe body of die block 10.

In pre-stressing die block 10, the outside surface of the core 13provides a supporting surface for the surface of the axial opening 11.The supporting surface of the core 13 must be harder or more rigid thanthe material of the die body 10 in order to support and sustain theprestressed condition of the die body 10. In addition, the supportingsurfaces of the core 13 must be yielding or elastic to react to a blowstruck on the surfaces 10A, 10B, 10C and 10D. A material foundsatisfactory when combined with a material having the physicalcharacteristics outlined above is an organic polymer having similarphysical characteristics as stated for the die block 10 with theexception that the durometer reading would be in the range of ninety andthe diameter of the core 13 would be approximately twelve percent (12%)greater than the diameter of the bore 11. In this manner the core 13would pre-stress die block 10 and provide a yielding supporting surfacefor the axial opening 11.

The ratio of the area of the bore 11 to the area of the mass 10 willvary according to the phyiscal characteristics of the organic polymerselected. With the physical characteristics specified above(representing Elastacast) the bore 11 approximates fifty percent of themass area of die block 10.

The diameter of the core 13 is larger than the diameter of the bore 11in order to provide a pre-stressed condition in the mass or die block10. The ratio of enlargement of the diameter of the core 13 to the bore11 controls the degree of compressible sensitivity in the mass or bodyof die block 10. This may be rephased as the degree of compressiblesensitivity in faces A, 10B, 10C and 10D.

Another factor governing the compressible sensitivity in die block 10 isthe relation of the durometer characteristics of the core 13 to themass. In the illustration the core has a durometer reading of (90)ninety and the die block has a durometer reading of (70) seventy. Toprovide a greater degree of compressible sensitivity in the die block10, the die block would be fabricated from an organic polymr having adurometer reading of sixty (60) or fifty (50).

The usual method of producing a die block 10 fabricated of an organicpolymer is by molding. A wide range in the physical characteristics oforganic polymers is commercially available but none duplicate thephysical compressible characteristics provided by pre-stressing.

FIGURES 1 and 2 illustrate a machine for producing a pre-stressedcondition in die block 10.

The machine, generally indicated by reference numeral 15, comprises aframe having side walls 16, 17 held in spaced relation by means of frontbrackets 18, 19 and rear brackets 20, 21. Angle iron feet 22, 23 arefastened to side walls 16, 17, respectively. A bottom platform 25provided with a central opening 26 is fastened on oppo site sides tofront bracket 18 and rear bracket 20. A top platform 27 provided onopposite sides with blocks 28, 29 is fastened on opposite sides throughblocks 28, 29 to front bracket 19 and rear bracket 21. Two pneumaticcylinders 30, 31 are fastened on one end to top platform 27 and on theother end to a flange 32 on the opposite end.

A piston head 33, provided with a piston stem 34, is slidably mounted inpneumatic cylinder with piston stem 34 slidably mounted in flange 32which is provided with a bore for that purpose. Similarly, a piston head37, provided with a piston stem 38, is slidably mounted in pneumaticcylinder 31 with piston stem 38 slidably mounted in flange 32 having abore for that purpose. A shelf 40 is fastened to the ends of pistonstems 34, 38.

A fixture comprising an upper plate 41 and lower plate 42 which are heldin spaced relation by means of rods 43, 44 is fastened to shelf 40 bymeans of the threads on a slide bar 45. Slide bar 45 is slidably mountedin flange 32 and top platform 27.

A mass of organic polymer material, illustrated as a rectangular dieblock 10 provided with an axial bore 11 having countersunk areas 12, isplaced upon bottom platform 25. A rod provided with an enlarged head 51is slidably mounted in bottom platform 25. Head 51 is passed throughaxial bore 11. Rod 50 is fastened in lower plate 42. Enlarged head 51 isslightly larger in diameter than the diameter of a core 13, so that core13 will easily slide into axial bore 11 through the path provided byenlarged head 51. A core 13 is placed between the top of enlarged head51 and upper plate 41. Piston heads 33, 37 are actuated in a manner wellknown to the pneumatic arts. Actuation of piston heads 33, 37,simultaneously forces core 13 into axial bore 11 as lower plate 42 pullsrode 50 and enlarged head 51 downwardly through axial bore 11.

One of the physical characteristics of an organic polymer is that itscompressibility is so negligible as to be disregardable in its use as adie block. Its non-compressibility is the essence of its superiority asa die set memher.

The enlarged diameter of core 13 forces the wall of axial bore 11 to bedisplaced. That displacement will be in the direction of the countersunkareas 12, so that the insertion of core 13 into bore 11 causes the massof die block 10 to shift and fill the space provided by countersunkareas 12. In this manner, as seen in FIGURE 5, the ends of the core 13are locked in bore 11 in the fashion of a rivet. The top and bottom ofdie block 10 are smooth, horizontal and parallel. In other words theexcess material created by the displacement of material in the wall ofaxial bore 11 caused by the enlarged diameter of core 13 is removed bycountersinking the ends of bore 11 before the core 13 is inserted intothe axial bore 11.

The insertion of the enlarged core 13 into the bore 11 increases theoutside dimension of die block 10 radially, because the organic polymermaterial is non-compressible.

FIGURES 7 thru 13 illustrate three practical applications in the use ofa pre-stressed die block 10.

FIGURES 7 and 8 illustrate a punch and die set. A punch and die set isan assembly consisting of an upper member called the punch holder and alower member called the die holder. The under surface of the punchholder and the upper surface of the die holder are those on which thepunch and die sections of a finished punch press tool are mounted. Inuse the die holder is clamped to the bed of the punch press, while theupwardly extending punch holder shank is fastened in the clamping holeprovided therefor in the sliding punch press ram. The tool is actuatedby the reciprocating motion of the ram. Mating guide posts and bushingsof an assembled die set assist in maintaining tool alignment during diesetting and the operation of the tool in the punch press.

These guide posts and bushings are employed in maintaining the punch anddie details in true alignment during ram-produced reciprocatory movementof the punch and punch holder relative to the die and die holder. Inconventional constructions, the posts are of plain cylindrical formationand are carried by and depend rigidly in relatively spaced order formdie holders.

The life of the punches and dies and the accuracy of the workaccomplished are directly affected by the accuracy of alignment of therespective moving parts of the punch and die set, and more particularlyby the manner in which this alignment is retained over a long period oftime.

In the past the bushings and the mating guide posts upon which thebushings slide or reciprocate were ordinarily tightly forced into holesdrilled into the punch holder and die holder, respectively. Of course,any alignment thus obtained is dependent upon the accuracy with whichthe holes into which the parts to be forced have been drilled. It iswell known that by the use of ordinary drills, it is hard to provideholes of any reasonable degree of accuracy, and that such holes can beobtained only by either separately reaming or boring the walls of theholes, with the consequent risk of inaccuracy in the separate holes. Itwas also necessary to grind the guide pins and the mating bushings oncenters and arbors, respectively, to insure absolute concentricity ofthe outside diameter of the guide pin and the outside diameter of themating bushings. These many and varied manufacturing operations causesinaccuracies in relative alignment of the guide posts and bushing holesin the holders as well as in the center distance between these holes. Arange of less than several thousandths of an inch was not ordinarily oreasily or economically obtained. This was especially true because of themethods of assembling the guide posts and bushings in their respectiveplates.

It is therefore an object of the present invention to provide a new andimproved punch and die set structure which is not subject to thelimitations, difiiculties and costs of manufacture above discussed, andwherein alignment is more radily achieved between the male member, thepunch, and the female member, the die. It is a further object of thepresent invention to provide an improved product as a result of themating of the punch and die, with a strip of metal to be worked, locatedtherebetween.

Referring to FIGURES 7 and 8 of the drawings, reference numeral 60designates the punch holder provided with a shank 61, and 62 designatesthe die holder, said parts being movably positioned with respect to eachother by guide pins 63, 64, carried by the die holder 62. Said guidepins 63, 64, being coaxial with and slidable within bushings 65, 66,respectively, carried by the punch holder 60.

A steel collar 67 having a chamber 68 is fastened to die holder 62, asby welding. Chamber 68 is of a shape to accommodate die block 10 in amanner wherein the walls of chamber 68 engage to support the sides 10B,10C and 10D and ends of die block 10, when slight pressure is exertedupon side 10A of die block 10. The core 13 in die block 10, in theexample of use illustrated in FIGURES 7 and 8 lies in a horizontal planeparallel to die holder 62.

A punch of preselected configuration is fastened to punch holder 60, inconventional manner, by use of dowel pins and screws (not shown). Astrip of metal 71 to be worked and therefore termed a work strip, isplaced upon die block 10. The ram of the press will force punch 70against work strip 71 and into die block 10, Where, due to thepreviously described physical characteristics of die block 10, a femaledie will momentarily be formed. In this manner the conventional femaledie and all of the attenuating manufacturing difficulties are totallyeliminated. It is apparent that with each stroke of the press the punchcreates a new female die element which confroms exactly to theconfiguration of the male punch element. Wear on the punch is mininized.The configuration of the work piece is sharp and exact. The work done bythe punch may be stamping, forming, drawing, severing or any otherconventional function performed by a punch in a conventional die set.The sensitivity of compression of the die block 10 to the stroke of thepunch 70 was previously described. The fact that the organic polymerfrom which the die block is fabricated is noncompressible but isdisplaceable, permits the contour of the punch 70 to be reproduced inthe die block 10 with the work piece sandwiched there between. Thefunctions performed by the punch with die block 10 include shearing.

In the illustration shown in FIGURES 7 and 8, a variation in the gage orthickness in the work piece 71 is of no consequence, due to thepre-stressed die block 10. However, where a metal punch is mated with ametal die to accommodate a work piece of a preselected gage; any largevariation in the gage of the work piece would result in a broken punch.

Reference is now made to FIGURES 9, 10, 11 and 12 wherein a new concept,function, construction and result are performed in a punch and die set.Punch holder 60A, shank 61A die holder 62A, guide pins 63A, 64A andbushings 65A, 66A are constructed identical to and function as describedwith reference to FIGURES 7 and 8. A steel collar 67A provided with achamber 68A is embedded at 67B in die holder 62A and is welded thereto,so as to withstand the strain thereon as will presently appear.

Chamber wall 68A may be provided with a preselected configurationillustrated as convoluted. A die block 10A, similar to die block 10,with the exception that is is round rather than square in horizontalcross-section, (compare FIGURE 6 with FIGURE 10).

Core 13A is located in a position at right angles or verticle to dieholder 62A, because the compressive force to be applied will compressdie block 10A in a manner to expand die block 10A radially to core 13A.

A metal tube 73 is placed in the chamber between the outside diameter ofdie block 10A and the convoluted chamber wall 68A.

A punch 70A in the preselected configuration of a disk having an outsidediameter, approximately equal to or slightly smaller than (see FIGURE12) the outside diameter of die block 10A, is fastened to punch holder60A by means of screws 74.

Reciprocating movement of the press will force punch 70A into die block10A thereby uniformly expanding die block 10A radially, thereby forcingtube 73 into convolutions of chamber wall 68A to produce a corrugatedcontoured tube.

As soon as punch 70A is withdrawn from die block 10A, the die block 10Awill return to initial pre-pressed position shown in FIGURE 11.

The reason die block 10A is able to perform the function of forcing tube73 into convolutions 68A is the non-compressibility of the organicpolymer controlled as to the extent of resilient sensitivity throughpre-stressing so as to expand uniformly or simultaneously throughout itsouter surface as contrasted to a rubber block which expands from theends toward the middle. The uniform expansion of die block 10A,simultaneously engaging tube 73 along its entire length prevents ruptureof the walls of tube 73, a condition which prevails when a die blockengages the tube 73 progressively from the ends toward the middle of thetube 73 if pre-stressing is absent or rubber is used as die blockmaterial.

Reference is now made to FIGURE 13 wherein is illustrated schematicallymechanism for embossing metal foil. A cylinder provided with the malecomponent of a rotating die is rotatively mounted upon a shaft 81. A dieblock 10B cylindrical in contour is pressed against cylinder 80 by meansof pressure rolls 82, 83, mounted, respectively, upon shafts 84, 85.

In the past cylinder 10B would be provided with the female matingcomponent to male component 80. Applicant substitutes a cylinder dieiblock 10B of a prestressed organic polymer with a smooth outer surfacefor the embossed female mating die component of the prior art. In thismanner applicant eliminates the complicated and expensive procedure ofproducing a mating female die for a male die component and at the sametime is able to provide sharper impressions on metal foil 88 passingbetween cylinders 80 and 10B.

Cylinder 80 is a driven troll. Cylinder 10B and pressure rolls 82, 83are idler rolls rotated through cylinder 10Bs engagement with cylinder80.

Having shown and described preferred embodiments of the presentinvention by Way of example, it should be realized that structuralchanges could be made and other examples given without departing fromeither the spirit or scope of this invention.

What I claim is:

1. The method of pre-stressing a metal forming die element mass oforganic polymer material of pre-selected hardness, comprising the stepsof providing an axial longitudinal passageway in said mass,pre-stressing the outside surface of the mass by forcing a core of adiameter greater than the diameter of said axial longitudinal passagewayand of a hardness greater than said mass into said axial longitudinalpassageway to fill said axial longitudinal passageway in order toproduce a pre-selected sensitivity to compressive resistance on theoutside surface of the mass.

2. A metal forming die element comprising a mass fabricated of anorganic polymer material having an axial longitudinal passageway ofpre-selected area, a core larger in area than said pre-selected area ofsaid axial longitudinel passageway, said core contained within saidaxial longitudinal passageway, said core being of a density greater thanthe density of said mass to provide a pre-stressed condition in saidmass to produce a pre-selected sensitivity to compressive resistance onthe outside surface of the mass.

3. A die block adapted to resist the compressive forces of a punchconsisting of a mass of material of preselected geometric shape andfabricated from an organic polymer, an axial opening of preselected areaprovided in said die block, a core larger in area than the area of saidaxial opening and contained within said axial opening and fabricatedfrom an organic polymer having a density greater than the density of thefirst mentioned organic polymer to provide a pre-stressed condition insaid die block and a preselected sensitivity to the compressive forcesof a punch.

4. A device to resist compressive forces comprising a mass of material,of preselected geometric shape, fabricated from an organic polymer, anaxial bore in said mass having an area approximately equal to one halfthe area of the entire mass, a core approximately ten percent largerthan said axial bore and fabricated from an organic polymer having ahardness approximately twelve percent greater than the hardness of thefirst mentioned organic polymer, said core contained within said axialbore to provide a pre-stressed condition in said mass with apre-selected sensitivity to compressive resistance in said mass.

5. A claim as recited in claim 4 wherein counterbored areas are providedat opposite ends of said axial bore in said mass and said core displacessaid mass to fill out said counterbores and provide locking means insaid mass for opposite ends of said core.

6. A device to resist compressive forces comprising a mass of materialof preselected geometric shape, and fabricated from an organic polymerhaving a durometer reading approximating seventy, an elongationpotential of approximately six hundred fifty percent an elongation oftwo hundred percent at eighteen hundred pounds per square inch pullingforce, a minimum tensile strength of fortythree hundred pounds persquare inch and an axial bore comprising approximately fifty percent ofthe area of the mass, a core approximately twelve percent larger in areathan the area of said axial bore and contained within said axial boreand fabricated from an organic polymer having a durometer readingapproximately ninety, an elongation potential of two hundred percent ateighteen hundred pounds per square inch pulling force, and a minimumtensile strength of forty-three hundred pounds per square inch, toprovide a pre-stressed condition in said mass of material.

7. A punch and die set comprising a punch holder provided with bushings,a die holder provided with guide pins coaxially aligned with saidbushings for relative sliding movement therebetween, a punch meansfastening said punch to said punch holder, a collar having a chamber ofpreselected contour, means fastening said collar to said die holder, amass of material of preselected contour to mate with the preselectedcontour of said chamber and located and supported in said chamber, andfabricated of an organic polymer, an axial bore of preselected areaprovided in said mass, a core larger in area than the preselected areaof said axial bore and contained within said bore, said core being of adensity greater than the density of said mass to provide a pre-stressedcondition in said mass and a mating die for said punch with apreselected sensitivity to the compressive forces of the punch.

8. A punch and die set comprising a punch holder provided with aplurality of bushings, a die holder provided with a plurality of guidepins coaxially aligned with said plurality of bushings for relativesliding movement therebetween, a punch, means fastening said punch tosaid punch holder, a collar having a chamber of preselected contour,means fastening said collar to said die holder, a mass of material ofpreselected geometric shape to mate with the preselected contour of saidchamber and located within said chamber, and fabricated from an organicpolymer, an axial bore in said mass having an area approximately equalto one half the area of the entire mass, a core approximately tenpercent larger than said axial bore and fabricated from an organicpolymer having a hardness approximately twelve percent greater than thehardness of the first mentioned organic polymer, said core containedwithin said axial bore to provide a pre-ssressed condition in said masswith a preselected sensitivity for the compressive resistance to theaction of said punch.

9. A claim as defined in claim 8 wherein said core lies in a planeperpendicular to the axis of the reciprocating movement of said punch.

10. A claim as defined in claim 9 wherein said core lies in a planeparallel to the axis of the reciprocating movement of said punch.

11. A punch and die set comprising a punch holder provided with aplurality of bushings, a die holder provided with a plurality of matingguide pins for relative sliding movement with said plurality ofbushings, a punch, means fastening said punch to said punch holder, acircular collar having an inner wall of preselected contour forming achamber, means fastening said collar to said die holder, a cylinderfabricated from an organic polymer and provided with an axial borehaving an area approximately equal to one half the area of the cylinder,a core approximately twelve percent larger in area than the area of saidaxial bore to radially increase the diameter of said cylinder, said corefabricated from an organic polymer having a durometer readingapproximately thirty percent greater than a durometer reading of saidfirst mentioned organic polymer, means fastening said cylinder to saiddie holder centrally located in relation to said inner wall and withinsaid chamber, one end of said cylinder and said core engageable withsaid punch whereby engagement of said punch in compressive action onsaid cylinder and core uniformly expands the outside surface of saidcylinder toward said inner wall.

12. The method of pre-stressing a mass of organic polymer materialcomprising the steps of forming the mass into a pre-selected geometricshape, providing an axial longitudinal passageway in said shape of anarea equal to one half the entire area of the shape, providing a core oforganic polymer material of a density of said first mentioned organicpolymer material and of an area approximately twelve percent greaterthan the area of said axial longitudinal passageway, providing said corewith a mating contour to the contour of said axial longitudinalpassageway, forcing said core into said axial longitudinal passageway toradially increase the size of said shape, whereby said shape becomespre-stressed and acquires a prese-' lected sensitivity to compressiveforces.

References Cited UNITED STATES PATENTS 2,572,215 10/1951 Swart.2,948,773 8/ 1960 Hawes. 2,966,872 1/1961 Schmocker 72-55 3,153,69710/l964 Faulkner 269229 X JAMES M. MEISTER, Primary Examiner.

U.S. Cl. X.R.

